An alternative would be to place in gic.h something like:
#ifdef CONFIG_CSRC_GIC
# define use_mips_gic_csrc gic_present
#else
# define use_mips_gic_csrc 0
#endif
Then the above code would be
if (!use_mips_gic_csrc)
return init_r4k_clocksource();
With less #if ugliness